Method of forming plural strip-shaped magnetic poles

ABSTRACT

To form strip-shaped poles in a preferably resilient magnet an electric conductor is provided in the direction of current flow with a plurality of parallel soft-iron strips on which the object to be magnetized is placed. A current pulse is passed through the conductor; the resulting magnetic field is highly directed by the strips. The device by means of which this method may be carried out is very simple and may comprise a hollow conductor on the inner or outer surface of which the strips are arranged.

United States Patent 1 Hofman 51 May 1,1973

[54] METHOD OF FORMING PLURAL STRIP-SHAPED MAGNETIC POLES [75] Inventor: Wytze Hofman, Emmasingel, Eindhoven, Netherlands [73] Assignee: U.S. Philips York,N.Y.

[22] Filed: Aug. 23, 1971 [21] Appl. No.: 173,904

Corporation, New

[30] Foreign Application Priority Data Aug. 31, 1970 Netherlands ..7012889 [52] U.S. Cl ..335/284, 335/306 [51] Int. Cl. ..H0lf 13/00 [58] Field of Search ..335/284, 302, 303

[56] References Cited UNITED STATES PATENTS 3,158,797 11/1964 Andrews ..335/284 3,335,377 8/1967 Kohlhagen ..335/284 3,474,368 10/1969 Seely ..335/284 3,191,106 6/1965 Baermann ..335/303 X Primary Examiner-George Harris Att0rneyFrank R. Trifari [57] ABSTRACT To form strip-shaped poles in a preferably resilient magnet an electric conductor is provided in the direction of current flow with a plurality of parallel soft-iron strips on which the object to be magnetized is placed. A current pulse is passed through the conductor; the resulting magnetic field is highly directed by the strips. The device by means of which this method may be carried out is very simple and may comprise a hollow conductor on the inner or outer surface of which the strips are arranged.

8 Claims, 5 Drawing Figures METHOD OF FORMING PLURAL STRIP-SHAPED MAGNETIC POLES The present invention relates to a method of forming a plurality of strip-shaped magnetic poles of alternating polarities on the surface of a permanent magnet to be magnetized, which surface is placed near a conductor, after which an electric current is passed through the conductor.

Such a method is described in a published German Patent application (Auslegeschrift) No. 1,489,805. In this method, the electric conductor comprises a plurality of parallel tortuous paths which are embedded in a synthetic resin. The effect is based on the presence of a magnetic field around this conductor. The magnet body which is to be magnetized is placed on the conductor and is polarized under the influence of this magnetic field.

The invention is characterized in that a plurality of strips of a soft -magnetic material are arranged parallel to one another in the direction of current flow and are interposed between the surface of the magnet and the surface of the conductor.

The conductors may have various shapes. A flat strip-shaped conductor may be used on one surface of which identical strips of soft-iron may be arranged across its full width.

Alternatively the conductor may be cylindrical, the soft-iron strips being arranged internally or externally along the entire circumference.

The advantage of this method is that the length of the current-carrying conductor is kept to a minimum, i.e., the conductor has a low electrical resistance. This is an important feature in view of the large values of the current pulses required to magnetize the magnet body (from 40 to 50 RA). The resulting accuracy of the polarization is high and the method may be carried out in a simple manner.

A device for carrying out the method which comprises a conductor through which an electric current may be passed according to the invention is characterized in that the conductor is provided with strips of a soft magnetic material which are arranged parallel to one another in the direction of current flow.

The invention also relates to a permanent magnet produced by the method. The permanent magnet preferably consists of a yielding synthetic material in which a permanent-magnetic powder is embedded.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIGS. 1 and 2 show a device for carrying out the method according to the invention,

FIG. 3 shows a detail of the magnetization and FIGS. 4 and 5 illustrate a cylindrical magnetizing device according to the invention.

Referring now to FIG. 1, the device shown comprises a flat copper electric conductor 1 on which a plurality of soft-iron strips 2 have been arranged parallel to one another. The magnetization of flat permanent magnets is effected as follows:

An object 3 to be magnetized, for example, a plastoferrite strip, is placed on or over the strips 2. A

current pulse, the direction of which corresponds to the arrow I, is passed through the conductor 1. In FIG. 3,

which shows such an arrangement in greater detail the current flows in a direction at right angles to the plane of the drawing and recedes from the reader. The current produces a magnetic field H, the direction of which is indicated by an arrow in the Figures. The softiron strips are magnetized by this magnetic field and have poles disposed as shown in FIG. 3. The field within the object 3 to be magnetized is indicated by broken arrows and produces magnetic poles at the boundaries of the strips 2.

A cylindrical conductor 1 also may be used. In FIG. 4, the strips 2 are arranged on the outer surface, and in FIG. 5 on the inner surface, of this conductor.

What is claimed is:

1. A method of magnetizing a permanent magnet to form a plurality of strip-shaped magnetic poles of alternating polarities on the surface of said permanent magnet which comprises, placing said magnet surface near an electric conductor, arranging a plurality of strips of a soft-magnetic material in parallel with one another between the surface of the magnet and the surface of the conductor, and passing an electric current through the conductor in a direction parallel to the magnetic strips.

2. A method as claimed in claim 1, characterized in that the conductor comprises a flat strip member on one surface of which identical strips of soft-iron are arranged across its full width.

3. A method as claimed in claim 1, characterized in that the conductor is cylindrical and the soft-iron strips are externally arranged along the entire circumference.

4. A method as claimed in claim 1, characterized in that the conductor comprises a hollow cylinder and the soft-iron strips are arranged along its entire inner circumference.

5. A method as claimed in claim 1 wherein said conductor comprises a flat member and said strips of softmagnetic material comprise identical strips of a softiron material juxtaposed across one surface of the flat conductor.

6. A method of magnetizing a magnetizable body to form a permanent magnet with a plurality of stripshaped magnetic poles of alternating polarity on the surface thereof which comprises, arranging a plurality of strips of a soft-magnetic material in a parallel between the surface of an electric conductor and the surface of the magnet, and passing an electric current through the conductor in a direction parallel to the magnetic strips.

7. A method as claimed in claim 6 wherein the magnetic strips are first arranged in parallel adjacent the surface of said electric conductor and then the magnetizable body is placed adjacent thereto so as to sandwich the magnetic strips between the electric conduction and the magnetizable body.

8. A method as claimed in claim 6 wherein prior to the step of arranging said magnetic strips between the conductor and the magnetizable body there is included the further step of impregnating a resilient synthetic material with permanent-magnetic powder to form said magnetizable body. 

1. A method of magnetizing a permanent magnet to form a plurality of strip-shaped magnetic poles of alternating polarities on the surface of said permanent magnet which comprises, placing said magnet surface near an electric conductor, arranging a plurality of strips of a soft-magnetic material in parallel with one another between the surface of the magnet and the surface of the conductor, and passing an electric current through the conductor in a direction parallel to the magnetic strips.
 2. A method as claimed in claim 1, characterized in that the conductor comprises a flat strip member on one surface of which identical strips of soft-iron are arranged across its full width.
 3. A method as claimed in claim 1, characterized in that the conductor is cylindrical and the soft-iron strips are externally arranged along the entire circumference.
 4. A method as claimed in claim 1, characterized in that the conductor comprises a hollow cylinder and the soft-iron strips are arranged along its entire inner circumference.
 5. A method as claimed in claim 1 wherein said conductor comprises a flat member and said strips of soft-magnetic material comprise identical strips of a soft-iron material juxtaposed across one surface of the flat conductor.
 6. A method of magnetizing a magnetizable body to form a permanent magnet with a plurality of strip-shaped magnetic poles of alternating polarity on the surface thereof which comprises, arranging a plurality of strips of a soft-magnetic material in a parallel between the surface of an electric conductor and the surface of the magnet, and passing an electric current through the conductor in a direction parallel to the magnetic strips.
 7. A method as claimed in claim 6 wherein the magnetic strips are first arranged in parallel adjacent the surface of said electric conductor and then the magnetizable body is placed adjacent thereto so as to sandwich the magnetic strips between the electric conduction and the magnetizable body.
 8. A method as claimed in claim 6 wherein prior to the step of arranging said magnetic strips between the conductor and the magnetizable body there is included the further step of impregnating a resilient synthetic material with permanent-magnetic powder to form said magnetizable body. 